These studies gather data on function of pituitary gonadal and pituitary thryroid endocrine systems in normal aging men in the Baltimore Longitudinal Study on Aging (BLSA), and data on daily reproductive hormone secretion patterns of normal cycling women comparing young and middle aged premenstrual females. Measurements of pituitary response to hypothalamic releasing factors as well as circulating levels of sex steroid hormones and their relationship to sexual behavior in aging men are being undertaken. Measurements of women's daily excretion of reproductive hormones is being used to follow events of the menstrual cycle.